<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script type="text/javascript">
    <!--
    document.write("Hello World!") //代码会被新浏览器识别，对于老式浏览器会忽略包括在注释间的代码
    //-->
</script>
</body>
</html>